Iain Armitage on the final season of

Iain Armitage, star of the CBS comedy “Young Sheldon,” has pulled off a magic trick: helping carry a network TV hit for seven seasons while also growing up. Luke Burbank talks with the young actor about the show’s finale; and with Jim Parsons (who created the character of Sheldon Cooper on “The Big Bang Theory”) and executive producers Steve Molaro and Steve Holland about the show’s success, which has surprised even them.